Many of the proposed projects involve manipulation of glycosylation and/or lectins in the hematopoietic or immune systems. In several instances, it is not possible to precisely predict the outcome in terms of alterations of blood cell development or of the immune response. Thus, the genetically-manipulated mice will first be analyzed by this Core facility using a standardized set of assays for the presence and function of the typical populations of blood cells and lymphocytes. These results will be corroborated with the hematological profiling done by Core D. Thereafter, the ability of some of the intact animals to mount specific types of immune and hematopoietic responses will be tested using a battery of defined challenges. The goal is to ensure that subtle alterations in the hematopoietic and immune systems are not missed. If complex abnormalities in hematopoiesis/immune function are found, elucidation of the underlying mechanisms will become a collaborative effort with the project leaders. This type of analysis is very important because the use of a few standardized assays can detect unforeseen immune and hematopoietic defects. As an example, mice lacking the beta isoform of protein kinase C (PKC) were not expected to have an immune defect. There is significant expression of several other PKC family members in lymphocyte populations, and functional redundancy between family members was the predicted outcome of genetic ablation of any one isoform. However, careful analysis of PKCbeta-mutant mice revealed a specific defect in a peritoneal lineage of B cells responsible for producing much of the serum immunoglobulins in the blood (l). In a second example, mice deficient for CD34, a highly O-glycosylated glycoprotein expressed on hematopoietic progenitor cells, appeared to possess the normal complement of blood cells. However, a few standard colony formation assays revealed significant deficiencies in several precursors in the hematopoietic compartment (2). Finally and most relevant to this program project grant, the gene disruption of the B cell lectin CD22 was recently shown to affect B cell responses in several assays of B cell function (3, 4, 4a).